Forming foamed polyurethane resins



2 Sheets-Sheet 1.

IN VEN TOR. JOIE/0f! J. ,Q5/5 J? AvmQA/fy Jan. 29, 1957 .1. J. REIS, JR

FORMING FOAMED POLYURETHANE RESINS Filed July 19, 1955 Jan. 29, 1957 J.J. REIS, JR 2,779,689

FORMING FOAMED POLYURETHANE RESINS Filed July 19, 1955 2 Sheets-Sheet 2V lNVE-NTOR JosfP/f ef/5, Je

FORMING FOAMED PLYURETHANE RESINS Joseph 3. Reis, lr., Pittsburgh, Pa.,assigner to Pittsburgh Plate Glass Company, a corporation otFennsyivaata Application luly 19, 1955, Serial No, @2,92%

l2 Claims. (Cl. 1l7-1ll4) This invention relates to the preparation ofsolid, resinous, teamed polyurethanes and it has particular relation tothe preparation of polyurethanes by the reaction of a diisocyanate and apolyester containing available hydroxyls and being the esteriiicationproduct of a .di carboxylic acid and one or more alcohols containing twoor more hydroxyl groups per molecule.

Valuable resinous materials have heretofore been prepared by reacting adiisocyanate, such as p-tolylene diisocyanate, or mixtures of isomers ofthe same, with a polyester of the alkyd type containing availablehydroxyl groups. Polyesters suitable for the purpose may, for example,be prepared by reacting a dicarboxylic acid, preferably one which isfree of ethylenic groups of the reactive type, with a dior polyhydricalcohol, or preferably with a mixture of alcohols, one of which isdihydric and another of which is polyhydric.

Wh-en the polyesters and a diisocyanate are brought together, especiallyin the presence of water, rapid reaction takes place with the generationof much exothermic heat, polyester molecules are bridged together bypolyurethane linkages and carbon dioxide is generated. The latter, underappropriate conditions, is entrapped in the mass to form polyurethaneresins of high cellularity valuable for many uses, for example, as slabsor panels with or without backings and constituting an insulatingmaterial adapted to retard the transmission of heat by conduction. Itmay also be employed as a cushioning material, as a filler for airplanePropellers, as a sound deadening material, as a covering or lining forpipes and other articles having non-planar surfaces. The generalcharacter of the reactions involved has been discussed in an article byO. Bayer et al., Rubber Chemistry and Tech nology, volume 23, pages 812through 835.

ln the preparation of resins and foams of the foregoing type, difficultyhas heretofore been experienced owing to the extreme rapidity of thereaction when the several components are brought together under reactionconditions. The reaction is so fast that the mixtures often tend to setup or resinify before adequate mixing of the several components can beattained. Also there is a tendency for the non-hornogeneous mixtureslocally to overheat with the formation of blow holes and other ,imeperfections.

Experiments have been conducted in which the polyester component and thediisocyanate component have` been mixed by applying them as separatesprays to the desired supporting surface or by otherwise distributingthem into each other as rapidly as possible as, for example, by passingthe two components through a turbomixer. It would appear that in manyinstances, the re action is so rapid that before adequate interminglingof the polyester component and the diisocyanate component can beobtained, the reaction has progressedso far that gels are formedprematurely or the diisocyanate in its reaction with the vseveralcomponents of the mixture to form gas undergoes reaction prematurelywiththe liberation of the gas at such stage :that much of it escapescomponent A termed a prepolymer.

2,779,689 Patented aan. 29, 1957 2 and the foam structure tendspartially' o1' completely to collapse.

rihe gels formed prematurely in the apparatus may tend to clog thelatter or to buildup upon the surfaces ot the same, thus necessitatingfrequent shut-downs for cleaning and rendering it difficult to stop arun without emptying and cleaning the apparatus in order to obviategelatina of residues while it is idle.

The reactions involved in polymerization and genera tion of gases in theoarnable mixtures are also highly exothermal and result in theproduction of much heat which tends to exaggerate or increase thepremature gelation and foaming reactions and at the same time, thetemperature may go so high as to produce objectionable decomposition ofthe product. Furthermore, the teur potatura tends to volatilize thediisocyanate component thus causing the loss of valuable material andtending to contaminate the atmosphere to create a hazard to the healthand comfort of the operators.

This invention is based upon the discovery that in the preparation offoamed polyurethane resins the foregoinCr diiiculties can be reduced orobviated by preliminarily reacting a portion of the polyester with thediisocyanate component in `such proportion as to provide a Theprepolymer is a relatively stable, sprayable or nearly anhydrous liquidwhich is capable of reacting with more polyester. The remainder of thepolyester is made up with a hydrating agent as a sprayable dispersion,but without diisocyanate and herein is termed component B. It too, inthe absence of isocyanate is stable. The two components (A and areseparately stored and when they are to be` mixed and teamed, they aresprayed. concurrently or sequentially as mists from separate oriticesupon a common surface. The two components are thus not commingled toform a highly reactive mixture until they are in desired position forcopolymerization and foaming. Therefore, premature foaming and gellingare obviated. The added polyester and water react quickly with theprepolymer product with the liberation of carbon dioxide to form a foamand with cross-linking reaction to convert the commingled materials intoa solid, durable state. The reactions are much the same in end productsas are obtained by mixing the whole of the polyester' with thediisocyanate and conducting the reaction in one stage.

ln the prepolymer, the diisocyanate is at least partially combined witha portion of the polyester so that the volatility thereof `is greatlyreduced and losses oi' diisocyanate are reduced with concomitantreduction of the health hazard and an increase in the comfort of the operators ot the apparatus. The prepolyrner mixes very readily with thedispersion of polyester when the two are brought together, thus reducinglocal overheating and other undesirable etects due to improper mixing.It will be apparent that the effects of overheating are furtherminimized because in the initial reaction to form the prepolymer, aconsiderable proportion of the total heat of reaction is given up, thuseiecting a distribution of the evolution of heat and reducing the peaktemperature resulting when` all components are reacted in a singlestage.

The techniques of this invention are adapted for preparation of eitheriiexible or rigid resins but are especially valuable in the preparationof more ilexible types.

The characteristics of some approved components which may be employed inthe practice of the present in-` vention Willtnow be described.

The polyester component The polyester components of the prepolymer andof the polyestermixture containing the water may be the armena same ordiierent. They are resins which are preferably of relatively highhydroxyl value and low acid value. They are soluble and liquid orfusible materials. The acid components of the polyesters preferably areof the dibasic type, or polybasic type and usually are free of reactiveunsaturation such as ethylenic groups or acetylenic groups. Theunsaturation, such as occurs in the rings of such aromatic acids asph-thalic acid, terephthalic acid, isophthalic acid or the like, isnon--ethylenic and non-reactive. These acids, for purposes of thepresent invention, may be regarded as being saturated. They may,therefore, be employed in the preparation of the polyesters hereindisclosed. Other non-ethylenic dicarboxylic acids free of reactiveunsaturation comprise those acids in which the carboxyl groups areinterconnected by open hydrocarbon chains. Suitable acids of this typeinclude succinic acid, adipic acid, sebacic acid, azelaic acid andothers containing up to about l() carbon atoms in the hydrocarbon chain.Mixtures of two or more of these acids may be utilized. In mostinstances, adipic acid is presently preferred either as the sole acidcompound or as a mixture with other dibasic acids such as the phthalicacids previously mentioned.

The alcohol component or components of the polyester contain a pluralityof hydroxyl groups and usually, though not necessarily, they comprise amixture of alcohols one of which is dihydric while the other contains atleast three hydroxyls. The dihydric alcohols may be selected from aclass such as the following:

Propylene glycol Dipropylene glycol Ethylene glycol Diethylene glycolPolyethylene glycol, or the like The second alcohol containing at leastthree hydroxyls may be selected from a. class comprising:

Glycerol Pentaerythritol Trimethylolethane Trimethylolpropane Mannitol,and others The polyesters containing a high percentage of dihydricalcohol component tend to be more flexible and thermoplastic. On theother hand, those alcohols such as glycerol, pentaerythritol, and thelike, containing three or more hydroxyls with dibasic acids, formpolyesters which upon reaction with diisocyanate tend to form hardthermoset foamed resins. By proper control of the ratios of the twotypes of alcohols, the cross-linking and therefore the hardness andthermosetting characteristics of the polyester-diisocyanate reactionproducts may be controlled. Polyesters containing only one type ofalcohol are not precluded. The proportion of the sum of the alcoholcomponents with respect to the acid components usually is substantiallyin excess of those commonly employed in the preparation of alkyd resinsand may be, for example, within a range of about to 50 percent excessover stoichionietric ratios. For tough, tiexible, resilient foamedproducts, a preferred molecular ratio of dihydric alcohol to alcohol ofhigher number of hydroxyl groups is about 18 to 1. This ratio decreasesinversely with increasing rigidity in the foamed product.

The esterication reaction employed in preparation of the polyester issubstantially conventional and comprises heating the mixture, with orwithout esteritication catalyst, in well known manner to a tempera-tureto effect evolution of water, but below that of substantial charting ordarliening of the product, e. g. to 250 F. to 400 F., or thereabouts.The reaction may be effected in the presence of a non-reactive diluent,such as xylene, which will distill azeotropically to assist in carryingaway the water of reaction. The reaction is preferably continued untilthe product is Viscous, but liquid, or at least becomes liquid when itis heated. The acid value usually is reduced,

often as low as practicable, for example, below 20 and preferably belowabout i2. Products of an acid value of 1 or below are obtainable and maybe advantageously employed in the preparation of rigid or tlexiblefoams. The ratios, hydroxyls to carboxyls are correspondingly high, forexample, in a range of 50 up to 500 or 600. Water of reaction isstripped from `the polyester employed in preparing the prepolymer,usually to such degree as to provide a substantially anhydrous product,or one which is as nearly anhydrous as is practical to obtain.A

Probably, in most instances, the residual water con-tent of thepolyester will not exceed about 0.1 or 0.2 percent and may besubstantially zero.

The diisocyfmate component The polyester may be mixed with a widevariety of diisocyanates in such amounts as to provide a substantialexcess of diisocyanate molecules as compared with the availablehydroxyls. Diisocyanates which may be interacted wth polyesters inaccordance with the provisions ofthe present invention contain the groupwhere R is aromatic, heterocyclic, aliphatic or a mixed group comprisingmoeties from two or more of these classes. Preferably, it contains fromabout 2 to 19 carbon atoms. The hydrocarbon group may also containchlorine or other substantially non-functioning groups. The followingconstitutes an illustrative group of diisocyanates which may be employedin the practice of the invention:

The p-tolylene dissocyanate or mixed isomers containing the same becauseof general availability and satisfactory operation in the process, arepresently preferred, though, of course, as commercial conditions changeor special requirements change, this preference is also subject tochange.

In preparing a prepolymer of a polyester and a diisocyanate inaccordance with the provisions of the present invention, it ispreferable that the polyester in the prepolymer be so proportioned thatapproximately 50 percent of the total thereof, e. g. 30 percent to 70percent, of the total is embodied in the prepolymer component. It isnecessary that substantially the total of the diisocyanate component beembodied in the prepolyrner fraction. The diisocyanate component of theprepolymer will vary in amount dependent upon the available hydroxyls inthe polyester. Usually the diisocyanate will be employed in a ratio toprovide about 2 to 5 moles of diisocyanate per molar equivalency ofcombined hydroxyls and carboxyls in the polyester of the prepolymercomponent.

A catalyst, which may be the same as is subsequently described, is alsoadded and the mixture of prepolymer components then reacts. Thepolyester and the diisocyanate will react to form a prepolymer with orwithout catalysts and with or without heating, but usually for purposesof this invention it is preferred to add catalyst and to apply butlittle or no extraneous heat. The heat evolved in forming theprepolymer, though considerable,`

is less than when the polyester and the diisocyanate are mixed inconventional manner (in the presence of water) in approximately theratlos desired in the .iinished product.

y, Thel catalyst In-order to prepare a` prepolymerof' the polyester andthe diisocyanate, in accordance with the provisions of the presentinvention, the two are mixed together. If desired, catalyst designed topromote the preliminary reaction between the two components is added.N-alkyl morpholine is presently preferred for this purpose, but may bereplaced by other catalyst, for. instance, the tertiary amines such astrimethyl amine, triethyl amine, dialkyl.- amino alcohol, or acommercial product sold as Etharneen-l8-15, which is understood to be atertiary amine in which the hydrocarbon chains are relatively long` oon-Etaining for example l0 to 18 carbon atoms per chain. If'prefcrred, thecatalyst may, as above stated, be omitted from the prepolymer phase,inasmuch as reaction between the polyester and the diisocyanate may beeffected in the absence of the same, either byheating the mixture or byallowing it to stand for a sulicient period of time.

Still other catalysis `which may be employed comprise quaternaryammonium compounds which under conditions of reaction are adapted todecompose to liberate tertiary amines in situ. Examples of suchmaterials are salts of tertiary amines such as N-methyl morpholine andanhydride-s of dicarboxylic acids such as acetic acid. These salts arereadily formed merely by bringing the reactants together.

By varying the .amounts of diisocyanates in the polyester, it ispossible to increase or decrease the viscosity of the polyesterprepolymer to suit speciiic conditions. The choice is intiuenced by thefunctionality of the polymer. v The prepolymer may comprise, forexample, from about 25 to 100y parts of diisocyanate, such as tolylenediisocyanate, per 10U parts of resin; or in event that a highly liquidprepolymer is desired, this. proportion of tolylenc diisocyanate may beincreased approximately to 00 parts. Rules for determining satisfactoryproportions in particular cases may be stated as follows.

The proportion of diisocyanate to polyester in preparation ofprepolymers or adducts is influenced by certain characteristics of theresin including hydroxyl number,

acidnumbcr, and water content; isocyanate equivalent isbascd upon these.For example, the resin of Example A in .column 6 has a combined hydroxylnumber and acid value of about 70. To obtain the isocyanate equivalentwe simply divide this number into 56,100.

:about SO=isocyanate equivalent This means that about 800` grams yofpolyester are needed for one mole .of an isocyanate or one half mole ofa diisocyanate. To be specific, 800 grazms of polyester is equivalent tograms tolylene diisocyanate. At least 1.00 percent excess diisocyanateis necessary to produce a suitable prepolymer,

Polyesters having' higher hydroxyl numbers, etc., will require higherproportions of diisocyanate. For example, a polyester withA zero acidvalue and a hydroxyl number of 400 will. require:

viscosity/fot they prepolyme-r, where the latter-is overly viscous forvmest.,effective` spraying; To thisl end; the N-methyl morpholine may beemployed in larger amounts.

thanJ are necessary for catalysis ofthe reaction,v Needless tolsay,N-Incthyl, morpholine maybeadded to prepoly- 111er after'its formation`and'` before mixing of the same.

with polyester emulsion, `by spraying. Amounts. thereof up. to 10 `or 12percent by. weight. based upon the polyester may be introducedatl-appropriate stages in the reaction.

If the catalyst is incorporatedw into the, mixture forming theprepolymer prior to reaction of said mixture, the catalystl promotesthe` formation of the latter and often the residual catalyst issuicient` to` attain the desired reactivity when the prepolymer issprayed with the emulsion of polyester upon :a suitable support. It isapparent that the catalyst may be in components A or B to the exclusionof the other, or it can be divided between the two components in anydesired proportion.

The prepolymer component, freeof water. and With-or without addedcatalyst, if desired, may-be and Vpreferably is incorporated with anappropriate emulsifying agent, such, as. is subsequently disclosed,`though` thisy component is not always required in part A` ot` thefoamable mixture, il it is presentin component B.

The water component Added polyester for; spraying concurrently with theprepolymer from a separate` spray orifice preferably is made up tocontain the water (either free or as a hydrated salt) necessary forcompletion of the reaction involved in the conversion of theprepolymer-polyester mixture upon the support into a foamed polyurethaneresin. The water may be employed as Water per se in an amount forexample of about l to 1Q` parts by weight per 100 parts ot` polyester.To facilitate the thorough commingling of the water with the polyesterin the second component of the foamable mixture, there is addedaneinulsifying` agent, such as Emcol-H-77, sold by the Emul'solCorporation and understood to be a liquid mixture of an anionic emulsierand a non-ionic emulsifier one being a polycarboxylic blend'and theother being a sulfonated fatty oil acid; Tween40 which. is understoodto. bea reaction product of ethylene oxide and polyoxyethylene sorbitanmonopalmitate; Tween 60 whichis understood to be a reaction product ofethylene oxide: and

sorbitan monostearate; Triton-X400 which is. understood to be acondensation `product of an alkyl phenol and ethylene oxide andothers'.

Use of excessive amounts of emulsifier dilutes the mixtureand theincreasel in emulsifying action is not commensurate with the other andoften undersirable effects attending `the usev of excesses. The water,if desired, may

` be replaced by a hydratingl agent or latent source of waterA such` asa hydrated salt as represented by the trihydrate of sodium acetate, thedecahydrate` or heptahydrate of sodium sulfate, (Glauberssalt), theheptahydrate of magnesium sulfate, or other agent which at thetemperatures attained in the reactions between the polyester and theprepolymer, liberate water in., situ. If` hydrated` salts are employedas a source of water, the amount thereof should be suicient to providewater in the afore-mentioned range.

The following constitute representative examples of polyesters which maybe employed in the preparation of prepolymers as component A and alsofor emulsii'lcation` with water or other hydrating agents to providepolyester component B` which maybe intersprayedr from separate orificesby the methods herein disclosed'to provide foamable and thermosettingcompositions.

EXAM-PLE Ae This-polyester was prepared from a mixture comprising:

Adipic acid 16 moles. Diethylene glycol 18 moles. Glycerolv 7.--1;mole.`

Catalyst (paratoly'lenesulfonic acid)- 0.1.` percentbased :l The mixturewas reacted in accordancelwith conventional procedures to form a liquidresin having a hydroxyl value in a range of 60 to 80 and an acid numberof l2 or less. The polyester is liquid in form. This polyester is ofrather low hydroxyl value and is often employed in forming more flexiblefoams. The glycerol of this polyester may be replaced in total or inpart by trimethylol propane. Similarly, the diethylene glycol may bereplaced by hexanediol. The polyester is useful in components A and B ofapplicants sprayable mixtures. Types of resins Well adapted for thepreparation of more rigid foams are represented by the following:

EXAMPLE B The resinifable mixture comprised;

, Moles Phth'alic anhydride 2 Adipic acid 10 Trimethylol propane 20 Themixture preferably is cooked to an acid value of about 1 and a hydroxylvalue of about 450. The resin is liquid and the high hydroxyl valuerenders it especially useful in forming components A and B of rigidfoams.

EXAMPLE 'C The resiniliable mixture comprised:

Moles Phthalic anhydride l Adipic acid 5 Glycerol 8 The mixturepreferably is cooked to an acid number of about l0. The polyester is ofhigh hydroxyl value and is a liquid product well adapted for mixing withdiiso cyanates, emulsifying agents and catalysts as herein dis closed.Components A and B may both be formed from this polyester. The foamedproducts of this polyester are of the rigid type.

EXAMPLE D A lpolyester was prepared comprising:

Moles Glycerol 7.6 Adipic acid 5.0 Phthalic anhydride 1.0

The mixture was cooked to an acid value of 42-46, a t.

hydroxyl number of 400 to 500 and a viscosity of 45,000 cps. to 100,000cps. It could be mixed with the diiso cyanates such as a mixture oftolylene diisocyanates to form a prepolyrner component A. A much higherproportion of isocyanate would be necessary. The polyester could bemixed with emulsifying agent, hydrated salt .such as the decahydrate orheptahydrate of sodium sullfate to form component B. The two componentscould be mixed by spraying and foamed.

EXAMPLE E A further liquid polyester comprising a fatty acid wasprepared. The polyester contained:

Moles Adipic acid 4 Phthalic anhydride l Oleic acid 2 Glycerol 8 Thepolyester may be used in components A and B of applicants mixture.

EXAMPLE F The polyester, when cooked, forms a polyester suitable for usein components A and B of the several foamable compositions hereinafterdescribed.

EXAMPLE G The polyester of this example embodied a mixture of phthalicanhydride andadipic'acid as the dibasic acid component. The polyhydricalcohol component comprised trimethylol propane. The proportions of theseveral ingredients were as follows: f

p Moles Phthalic anhydride l Adipic acid 5 Trimethylol propane 9.2

The product was cooked to a fhydroxyl value of 473 and an acid value ofapproximately 1. This polyester is very well adapted for use ascomponents A and B of rigid foams.

Any ot' the polyesters of the foregoing Examples (A through G) may beincorporated with a diisocyanate such as tolylene diisocyanate in anamount to provide a liquid, sprayable prepolymer which amount usuallywill involve diisocyanate in a range of about 20 to 600 parts per 100parts of polyester dependent upon the fluidity desired in the prepolymercomponent. Where the proportion of diisocyanate is very high, the excessdilutes the polymer and promotes uidity thereof.

The following constitutes a generalized formulation of a prepolymer(component A) prepared in accordance with this invention:

Parts by weight Polyester 100 Diisocyanate 20-600 Catalyst 0-20.Emulsitier 0-5 The polyester-water dispersion (component B) may begeneralized as follows: l

Parts by weight Polyester 100 Catalyst 0-10 Emulsier 0.1-10 Water (freeof latent) l 0.1-10

EXAMPLE I The polyester in this example corresponded to that disclosedin Example A. This polyester was of a hydroxyl value of 60 to 80 and wasof an acid value of about 3. For purposes of preparing a prepolymer, amixture was prepared comprising:

Parts by weight Polyester (Example A) 100 Tolylene diisocyanate(Mondur-TD) 100 N-methyl morpholine (catalyst) 2 Emcol-H-77 (emulsifier)2 This prepolyrner from the mixture may be sprayed at once, but may bestored for several days at room temperature or longer underrefrigeration. The prepolymer is a liquidproduct of a viscosity adaptingit for spray' applica tion by a conventional spray gun.' This prepolymer`con stitutes component (A) of applicants spray system. The polyestercomponent (component B) of the'spray system vwas made up as 'a liquid,sprayable dispersionzas "renews:

Y Parts by weight Polyester (Example A). 100. N-methyl morpholine 2.Emco1-H-77 2. Water 1 to 3 (preferably 2).

Components A and B of the system are maintained in separate containersand when it is desired to spray them upon a surface or into a mold, theyare discharged through separate conduits having orifices which dischargethe two concurrently so that the droplets as they strike the surface arecompletely and thoroughly intermixed. In the sprayingV operation, a pairof spray guns, one for each liquid (A or B) may be employed, the spraysbeing directed upon the same spot. However, for manual operations it isusually preferred to employ a single spray gun having separate feedlines and separate orifices `for each line.

EXAMPLE 1I it has also been found practicable to incorporate with thepolyester component of the prepolymerizable mixture certain compatibleresins such as a phenolic resin in an appropriate stage ofpolymerization. In an illustrative example, a Bakelite resin soldcommercially as Bakelite-B-R-Q-l8759 was incorporated with a polyesterwhich was substantially the same as that of Example A. The phenolicresin was employed in an amount of about 5 parts per 100 parts of thepolyester. The range of the phenolic resin to polyester may convenientlyextend from l part to 25 parts per 100 parts of said polyester with apreferred range being from about 5 to l0 parts. The polyester and thephenolic resin may merely be dissolved in each other or if preferredthey may be conjointly polymerized, for example, by adding the phenolicresin to the reaction mixture employed in the preparation of thepolyester and then cooking the mixture to effect esterication reaction.The polyester, when so modified, may be employed in the preparation ofthe prepolymer as in Example l. Likewise, the modified polyester may beemployed as component A constituting one of the sprayable mixtures asdisclosed in` the preceeding example. The two components (A and B) afterapplication by spray to an appropriate support, may be foamed and curedto a solid, resinous state in the usual manner. The presence of thephenolic resin modifier is sometimes advantageous, inasmuch as it hasbeen found that it substantially reduces any tendency of the foamablemixtureto form puff spots or large bubbles between the resin and thesupporting surface.

The components A and B of applicants interpolymerizahle mixture,respectively comprising prepolymers of polyesters and diisocyanates andemulsions of polyesters and a hydrating agent, are susceptible of use invarious types of apparatus. It is prerequisite that the two componentsbe kept separate from each other until they are in their final positionupon the surface to be treated or in the mold and that they then bemixed substantially instantaneously as the layer thereof is built up.They may be applied in job operations as, for example, upon isolatedindividualobjects such as parts of buildings and other articles. Theymay also be employed to coat a continuous succession of articles or astrip article upon a moving conveyor.

Illustrative embodiments of apparatus adapted for use in applying foamsto various articles or for forming foams as a discrete material arediagrammatically illustrated in the drawings inwhich:

Fig. 1 is a tiow diagram of a system for applying concurrently a sprayof an aqueous emulsion of polyester and a prepolymer of a polyester anda diisocyanate; and

Fig. 2 illustratesone type of spray apparatus which may be used inapplying the ftwo components to a surface and` thetconcurrentapplication of components A and B1 to a surface by use of saidapparatus.

In the process and apparatus as illustrated` in Fig.- 2

of the drawings, an article such as awall of a building embodyingopposed rigid curtain elements 20 and 21 heldV in spaced relationship byframing elements 22 is shown as being provided with a foamed layer ofpolyurethane resin, as indicated at 23. The apparatus employed in theoperation comprises a pair of slightly convergent nozzle tubes 224i and26 which may be of conventional design and are provided with heads asindicated at 27 and 2E designed to deposit the material being sprayed inan appropriate pattern. The tubes are further provided with valves suchas needle vales 29 and 31, designed for regulating and metering the flowof air through the tubes. The tubes are also connected as for example bymeans of iiexible tubes or hose 32 and 33 to a pair of pumps, indicateddiagrammatically at 34 and 36 as being variable delivery pumps. Thepumps are positively mechanically connected together as by a commondrive (not shown) to provide a duplex pump designed accurately andpositively to proportion the feed of components A and B to theirrespective nozzles. However, each pump may also be separately driven.Since suitable proportioning pumps are commercial articles, it is notdeemed necessary to describe fthe mechanism thereof. Positivedisplacement gear pumps such as are often employed in spinning rayon aresuitable.

The pumps are also provided with connections 32a and 33a leading toreservoirs (not shown) for the respective components.

Thel two tubes (24 and 26) are cross connected by a bar 3'? which may betubular and being designed to discharge gaseous medium into the tubesfor purposes of breaking up the components passing through the tubes,and to deliver them as ne sprays from the heads 27 and 28.

The apparatus is shown as comprising a handle 38 adapted to be graspedmanually and being connected to the transverse bar 37. it is providedwith a tube (preferably flexible) Sii for the supply of air, carbondioxide, or other gaseous medium to the tubes 24 and 26 for impellingand breaking up the liquids from the nozzles. The pumps and/ or theirhose connection may be provided with jackets (not shown) for a` heating;medium or for electrically heated mantles by means of which the liquidscan be brought to and maintained at precisely the optimum viscosity forspraying. Such jackets or mantles for purposes of simplicity, have beenomitted from the drawings.

A suitable iiuid pressure operated switch indicated at S for controllingthe pump motor current may also be disposed in one of the conduits 32,33 or 39 so that when the apparatus is not spraying, the back pressurein the system shuts off the motor or motors. The apparatus may also beprovided with trigger valves or other valve mechanism which canconveniently be operated for purposes of shutting off the ow of liquidsand air when desired. Since the elements are conventional, it has notbeen deemed necessary to show them in detail.

It is to be observed that the two spray tubes 2,4 and 2e are disposed inslightly convergent relationship so that insofar as practicable thesprays converge at the proper distance thus tending to intermix thedroplets very thoroughly and substantially as they strike the supportingsurface, namely thecurtain Ztl. However, complete intermixing of thesprays while they are in transit to the surface is not essential sinceadequate mixing of the droplets from the two nozzles may be obtained byreciprocating the sprays across the surface in such manner that thoroughoverlapping thereof `is obtained. it will be recognized that the sprayscomprising minute droplets from the two nozzles, as they strike withconsiderable force upon the surface undergoing treatment, are adequatelyand uniformly dispersed in each other so that highly uniform foaming cantake place without any undue tendency Vof the foamable mixture locallyto overheat. i

-The normal atmospheric temperature, especially when accompanied by theexothermal rise characterizing the interpolyrnerization between theprepolymer and the polyester emulsion is adequate to cure the mixturewithin a reasonable time. This is especially true in those instanceswhere one or both components A or B contain an efficient catalyst ofinterpolymerization such as an N-alkyl morpholine, such as N-methylmorpholine. rThe mixture within a very short time after application willbeg-in to foam and to gel and ultimately, if allowed to stand even atatmospheric temperature, will cure to provide a foam which is flexibleor rigid, dependent upon the components and the proportions thereof. Ifdesired the curing rate can be further accelerated by application ofheat such as radiant heat to the surface.

The process is illustrated as being applied to the coating of a wallsuch as that of a building or of a cabinet. However, it will be apparentthat the same apparatus and technique may be employed to the coatings ofvarious other articles where, by reason of isolation, or by reason ofthe small number of articles to be treated, it is not commerciallypracticable to employ a more elaborate system such as is capable ofcontinuous operation in treating a multiplicity of articles or acontinuous band or web of material.

A further elaboration of the apparatus illustrating more completely ageneral system for use in spraying the prepolyrner and polyester inaccordance with the provisions of the present invention to form afoarned polyurethane resin is illustrated in Fig. l of the drawings. Inthis embodiment of apparatus, prepolymer and a dispersion of polyesterare contained respectively in pressure pots 50 and 51. These pots are ofconventional design and are closed so that a gaseous medium, such as airor carbon dioxide, under pressure can be confined above the liquid inthe pot. Gauges indicated at 52 and 53 provide convenient means forchecking the pressure from time to time. Gaseous medium is supplied tothe pots respectively by air lines 54 and 56 having constant pressureoutlet valves 57 and 58 disposed therein. Lines 54 and 56 are connectedto a supply line 59 leading to a source of gas under pressure (notshown). Outlet lines 6l and 62 from the pressure pots lead to variabledelivery pumps 63 and 64- which may be driven by a common motor or byseparate motors (not shown) as may be desired and which function asmetering means to supply prepolymer and polyester components in properproportions with respect to each other. P

Means automatically to start and stop the motors or the pump isindicated diagrammatically as comprising, `a

uid operated switch known as a Pressuretrol switch 65 which is connectedby a line 65a with one of the fluid conducting lines, e. g. line 66 sothat when the pressure in the line goes up, due to the stopping of thespray gun (to be described), the switch is opened. The switch may beconnected directly in the circuits of the motor, or they may beconnected in circuit with conventional motor starters 65h which startand stop the motor when the switch 65 is operated by changes of pressurein the fluid conducting lines, e. g. line 66. When the pressure in thesystem drops owing to the opening of the valves of the spray gun, theswitch 65 is closed to start the motor and thus to effect the flow offluids in the system, forming the sprays.

It is to be recognized that in some instances, the prepolymer and thepolyester are relatively viscous and in order yto reduce the viscositythereof to a value suitable for spraying operations, it may be`desirable lto warm one or both of them. For this purpose the feed linesd6 and 67 are discharged into conventional heat exchangers 68 and 69.The heat exchangers are provided with inlets 71 and outlets '72 for thecirculation of a heated medium such las water cr the like. In a specificexample, this medium is maintained at a temperature of about 160 F.which is found to be adapted to maintain the prepolymer and polyestercomponents as disclosed herein at a satisfactory viscosity. Obviously,this temperature may be varied dependent upon the viscosity desired inthe spraying operation and also depending upon the inherent viscosity ofthe prepolymer and polyester employed.

Prepolymer and polyester' are respectively discharged from the heatexchangers through hose connections 73 and 74 which` as indicated at 76and 77, are provided with flexible jackets. These jackets, in theembodiment shown, comprise flattened elongated -strips of rubber orother flexible plastic having three channels '73, 79 and Si) extendinglongitudinally lthereof. The hose connections are strung through .thecentral channel Sil. The side channels indicated respectively at '78 and79 in each of the jacket elements provide means for the circulation ofthe heated medium through the jacket. Channels 79, as indicated arejoined to T-connections Sl which are further joined to the inlets 7l ofthe heat exchangers and to supply lines SZ through which heat transfermedium is circulated simultaneously to the heat exchangers and to thehose connections. The channels i8 and '79, at the ends opposite theinlet for heat transfer medium, are cross connected by tubes S3 of metalor other suitable material so that heat exchange medium flowing upthrough the channels 79, crosses over through the tubes 33 anddischarges through outlet tubes 84.

Tubes 73 and 7d after passing through the heated jackets discharge intospray gun tubes 86 and S7 which are identical with the tubes 24 and 26already described. Further description thereof is not deemed to benecessary at this time. The gaseous medium under pressure is alsosupplied to the spray gun through a tube or hose line 88 having aconstant pressure outlet valve 89 disposed therein and further beingconnected to the line 59 thus supplying gaseous medium under pressure tothe spray gun in order to break up the prepolymer and the polyestercomponents into relatively ne sprays which as they strike ian article tobe coated, are thoroughly intermixed thus promoting uniform foaming andpolymerization of the mixture.

I claim:

l. ln a method of forming a polyurethane resin foam upon a solidsurface, the steps of spraying from separate orifices (A) a liquid,anhydrous, sprayable, relatively stable prepolymer of a diisocyanate anda polyester of an alcohol containing at least 2 hydroxyls and adicarboxylic acid and (B) an aqueous dispersion of a polyester which isalso an alcohol containing at least 2 hydroxyls and a dicarboxylic acid,impinging the two sprays upon said surface and effecting foaming andcuring of the resultant mixture.

2. In ia method of forming a polyurethane resin foam upon a solidsurface, the steps of spraying from separate orifices (A) a sprayableliquid, anhydrous, relatively stable prepolymer of a diisocyanate and apolyester of an alcohol containing at least 2 hydroxyls and adicarboxylic acid and (B) a dispersion comprising a polyester which isalso of an alcohol containing at least 2 hydroxyls and a dicarboxylicacid, water and an emulsifying agent and impinging the two sprays as anintimate mixture upon a common surface and effecting foaming and curingof the mixture.

3. In a method of forming a polyurethane resin foam upon a solidsurface, the steps of spraying from separate orifices (A) a liquid,anhydrous, sprayable, relatively stable prepolymer of a diisocyanate anda polyester of an alcohol containing at least 2 hydroxyls and adicarboxylic acid and (B) an aqueous dispersion of a polyester which isalso of an alcohol containing at least 2 hydroxyls and a dicarboxylicacid, one of said components A and B containing a catalyst of reactionbetween a diisocyanate and an alcohol, impinging the two sprays as anintimate mixture upon` a common surface and effecting foaming and curingof the mixture.

4. The method of claim 3 in which the catalyst is a lteritiary amine.

5. The method of claim 3 in wh-ich the `catalyst is an N-alkylsubstituted morpholine.

6. In a method of forming a polyurethane resin foam upon a solidsurface, the steps of Vspraying from separate orifices (A) a liquid,sprayable, anhydrous, relatively st-able prepolymer of a diisocyanateand a polyester of an alcohol containing a-t least 2 hydroxyls and analcohol and (B) a dispersi-on of (l) a polyester whi-ch is also of. analcohol .containing at least 2 hydroxyls and a dicarboxylic acid (2)Water and (3) a dispersing agent, one of the components A and Bcontaining a catalyst of form-ation of polyurethane resin, impinging thesprays from the two -oriices as au intimate mixture upon the solid sul--face and effecting foaming and curing of the mixture.

7, The method of cla-im 6 in which the catalyst is an N-alkylmorpholine.

8. In a method of forming a polyurethane resin foam upon a solidsurface, the steps of spraying from separate orifices (A) a liquid,anhydrous, sprayable, relatively stable prepolymer of a diisocyanate andan alcohol containing at least 2 hydroxyls and adipic acid and (B) anaqueous dispersion of a polyester which is also of an alcohol containingat least 2 hydroxyls and adipic acid, the latter polyester furthercontaining a dispersing agent and an N-alkyl morpholine, collecting thetwo sprays as intimate mixtures upon said surface and eecting foamingand curing of the mixture.

9. In a method of forming a polyurethane resin foam upon a solidsurface, the steps of spraying from separate orifices (A) a diisocyanateand a polyester of an alcohol mixture comprising a dihydric alcohol andan alcohol containing at least 3 hydroxyls and adipic acid and (B) anaqueous dispersion of a polyester which is of an 1'4 alcohol containingat least 2 hydroxyls and a dicarboxylic acid, said dispersion containingan N-alkyl morpholine, impinging the sprays as an intimate mixture upona common surface and effecting foaming and curing of the mixture.

l0. The method of claim 9 in which. the diisocyanate is p-tolylenediisocyanate.

11. The method of claim l0 in which the dihydric alcohol is diethyleneglycol.

12. ln a method of forming a polyurethane resin foam upon a solidsurface, the steps of emitting from separate couvergently directedorifices (A) a sprayable, liquid, anhydrous, relatively stableprepolymer of a diisocyanate and a polyester of an alcohol containing atleast two hydroxyls and a dicarboxylic acid and (B) an aqueousdispersion comprising a polyester `which is also of an alcoholcontaining at least two hydroxyls and a dicar boxylic acid and formingthe two components into a spray which is a mixture of the two componentsand collecting said spray upon said solid surface as an intimate mixtureand effecting foaming and curing of the mixture.

References Cited in the tile of this patent UNITED STATES PATENTS'2,450,503 Drummond oer. 5, 194s 2,602,783 Simon July 8, 1952 2,634,244Simon -2 Apr. 7, 1953 2,650,212 Windemuth Aug. 25, 1953 2,657,151 GenselOct. 27, 1953 FOREIGN PATENTS 700,611 Great Britain Dec. 9, 1953 700,617Great Britain Dec. 9, 1953

1. IN A METHOD OF FORMING A POLYURETHANE RESIN FOAM UPON A SOLIDSURFACE, THE STEPS OF SPRAYING FROM SEPARATE ORIFICES (A) A LIQUID,ANHYDROUS, SPRAYABLE, RELATIVELY STABLE PREPOLYMER OF A DIISOCYANATE ANDA POLYESTER OF AN ALCOHOL CONTAINING AT LEAST 2 HYDROYLS AND ADICARBOXYLIC ACID AND (B) AN AQUEOUS DISPERSION OF A POLYESTER WHICH ISALSO AN ALCOHOL CONTAINING AT LEAST 2 HYDROXYLS AND A DICARBOXYLIC ACID,IMPINGING THE TWO SPRAYS UPON SAID SURFACE AND EFFECTING FOAMING ANDCURING OF THE RESULTANT MIXTURE.